1. Field of the Invention
The present invention relates to an optical communication technology, and more specifically, to an optical device in which an optical waveguide and an optical fiber are optically coupled.
2. Description of Related Art
In optical communication, an optical signal in a silicon optical waveguide is required to optically couple to an optical cable on the outside of the waveguide. A grating (diffraction grating) structure created inside the slab structure of the silicon optical waveguide is often used to focus and couple the propagating light onto the core of an optical fiber. A schematic view of this type of optical device is shown in FIG. 1.
FIG. 1 (a) is a cross-sectional side view of the optical device 10, and FIG. 1 (b) is a plane view from below. In the optical device 10, an oxide layer (silicon oxide, silicon oxynitride or silicon nitride) 12 is provided on a silicon substrate 11, and a silicon optical waveguide 13 is formed on the oxide layer 12. A grating coupler 14 is also formed at one end of the silicon optical waveguide 13. In the grating coupler 14, a plurality of approximately concentric circular grooves are provided in parallel. An optical beam focused by the grating coupler 14 is aligned onto the core 15 of an optical fiber 16, and optical coupling is performed between the silicon optical waveguide 13 and the optical fiber 16.
In JP2002-357737A, an optical fiber guiding portion is formed in one surface of a glass substrate so as to optically couple an optical fiber with the glass substrate. A lens, the center of which is aligned with that of the optical fiber guiding portion, is formed on the other surface of the glass substrate, and the light passing through the glass substrate is focused by the lens onto the core of the optical fiber.
In JP05-241044A, an optical waveguide is cut so that an inclined surface is formed at the deflection point of the optical waveguide with respect to the surface of the substrate on which the optical waveguide has been formed. Light is reflected by the inclined end surface. A lens is formed on the optical waveguide in the vicinity of the inclined end surface, and the light reflected by the inclined end surface is focused by the lens and directed towards an optical element.